Just program your scanner to cover the 418.000 range. You'll hear the ARTC transmissions, plus GWA. Take note that from around the middle of next year the ARTC are switching to the digital network, as have, and will, other operators. That will reduce the amount of rail transmissions you'll be able to receive on your scanner.
You have not wasted your money. Despite the fact that ARTC will be switching to the Next G platform, there will still be a significant amount of traffic to be heard.
The Next G system will be for train control, yards, depots and mainline shunting will still be on the conventional channels.
Also at this stage QR is not too impressed with the new systems and will be sticking with its analogue conventional radio network for a little time yet - smart move in my humble opinion.
Nevertheless, enter between 418.1000 and 420.000 MHz, the majority of rail radio traffic is in this portion of the band. Naturally some small operators have allocation outside it.